Asian invader hits N.S. waters

Invasive seaweed already out of control off New England, scientist says

An invasive seaweed that has choked the ocean bottom off parts of New England has been found in Nova Scotia.

A team of marine biologists found four strands of H. japonica, which originates in Asia, while collecting seaweed samples off Upper Blandford in Mahone Bay.

While the discovery in August came as a surprise to team leader Gary Saunders of the University of New Brunswick, he is well-acquainted with H. japonica.

Just a few months before the Mahone Bay expedition, he observed an infestation of the red, branch-like algae while diving off northern Massachusetts.

“You couldn’t see any other algae on the bottom,” Saunders said Thursday in an interview from New Brunswick. “This stuff was on top of everything.”

It was his genetic testing lab that confirmed in 2007 that H. japonica had migrated to North America. The UNB lab analyzed samples collected by a marine biology team from Northeastern University in Boston.

Saunders expected the algae would eventually show up in Canada — but not this quickly.

“Ironically, I gave a talk last May (in Nova Scotia), and I predicted it would be here in four or five years, so it wasn’t even on our radar.”

The Asian invader has definitely caught the attention of coastal residents in Massachusetts. A recent article in the Boston Globe describes shorelines blanketed by the seaweed, which gives off an overpowering, sewer-like odour.

The algae has also been a headache for New England fishermen, whose traps and lines have been covered by the spreading algae. Besides the inconvenience to humans, the spread of any invading ocean plant can have profound consequences for the local ecosystem, Saunders said.

H. japonica grows on top of existing seaweed species, which represent an important food source for small invertebrate animals. If invertebrates can’t get to their food and the population is reduced, that means less food for the animals up the food chain such as fish.

“You’re talking about changes at the most basic level,” Saunders said.

The UNB team alerted Fisheries and Oceans Canada as soon as the discovery was made. A Bedford Institute of Oceanography spokesman said the department is monitoring the situation. The crucial question will be whether the seaweed can survive the winter in Canada’s cold ocean waters and take hold permanently, Carl Myers said in an interview.

Fisheries and Oceans will place monitoring stations in Mahone Bay in the spring and staff divers will search for the seaweed, Myers said.

James Mood, a retired lobsterman and head of a fishing association in Yarmouth, said sea plants such as lemon weed are well-known nuisances to Nova Scotia fishermen.

“When it breaks loose, your lobster trap will fill full of lemon weed, and that stops the lobster (from coming in),” Mood said from his home in Lower Woods Harbour on Thursday.

“You never know what’s happening with Mother Nature. She’s been good to us, but she can also be bad to us.”

A scientist who works for a Nova Scotia company that harvests seaweed said the H. japonica discovery was interesting but not alarming.

Alan Critchley, vice-president of research with Acadian Seaplants, said the algae represents more of a nuisance to industry compared with plant species that contain toxins. “I would have no issues about its safety in terms of its existence in the local environment,” Critchley said.

The seaweed likely also wouldn’t compete with the products harvested by Acadian Seaplants, mainly rockweed and Irish moss. However, the company plans to monitor the situation, Critchley said.